Impact-modified polycarbonate-molding compositions which are suitable for extrusion applications are known. EP-A 0 345 522 (U.S. Pat. No. 5,061,745) describes compositions containing aromatic polycarbonates, ABS-graft polymers and/or copolymers that contain styrene rendered fire-retardant by the incorporation of mono phosphoric acid esters. Corresponding compositions rendered flame retardant by the incorporation of oligo phosphoric acid ester or mixtures of oligo- and mono phosphoric acid esters have been disclosed in U.S. Pat. Nos. 5,204,394 and 5,672,645. Also relevant is the disclosure JP-A 111 997 68 of PC/ABS-mixtures that are made fire-retardant with the incorporation of monomer and oligomer phosphoric acid esters. The fire-retardance is improved distinctly by the inclusion of inorganic fillers, such as talc. The inclusion of inorganic filler adversely affects the mechanical properties, especially the toughness of polymer blends.
U.S. Pat. No. 5,849,827 and WO 99/07782 disclosed PC/ABS-molding compositions that are rendered fire-retardant by the inclusion of oligo phosphates based on resorcinol and on Bisphenol-A. The after-burning time periods are reported to be significantly reduced by adding small amounts of nano-scaled inorganic materials. The melt stability of these compositions is deemed insufficient for extrusion applications.
WO 99/57198 describes PC/ABS-molding compositions that are made fire-retardant by the incorporation of an oligophosphate derived from resorcinol and fluorinated polyolefin. Linear and branched polycarbonates having high molecular weights (31,000 and 32,000 g/mole) were used in these compositions. The rheological properties of these compositions (MVR) make these compositions suitable for extrusion. WO 01/66634 (corresponding to US2003092805) describes molding compositions that contain polycarbonate, an impact modifier and a halogen-free phosphorous flame-retardant and optional inorganic filler. These compositions are characterized by their combination of good fire-resistance and melt viscosity at 260° C. and a shear rate of 100 s−1 to ≧600 Pas.
WO 00/58394 disclosed polycarbonate molding compositions containing graft polymers and oligo phosphate. WO 01/48074 disclosed compositions containing polycarbonate, impact modifier, phosphorous-containing fire-retardant and talc of high purity. WO 01/48087 describes compositions containing polycarbonate, impact modifier and talc having Al2O3-content of <1 weight %.
WO 01/66635 describes compositions containing polycarbonate, impact modifier and phosphorous fire-retardant. Extrusion-grade melt-stable, flame retardant, impact modified polycarbonate compositions that are suitable for thermoforming and articles made therefrom have not hitherto been disclosed.
To be suitable for use in e.g. the automotive industry, fire-resistant polycarbonate compositions need to combine high mechanical strength, including strength at low temperatures and exceptional fire-resistance.
An object of the invention therefore is the development of an impact-modified, fire-retardant extrusion-grade, thermo-formable polycarbonate composition having good mechanical properties and surface quality.